The invention relates to internal combustion engines, and more particularly to internal combustion engines used in outboard motors. The invention also relates to catalyst apparatus used in connection with internal combustion engines.
A prior art internal combustion engine 1 is illustrated in FIGS. 1 and 2. The engine 1 is a two-cylinder, two-cycle engine used in an outboard motor. The engine 1 includes a cylinder block 2 defining upper and lower cylinders 3 and 4 having (see FIG. 2) respective upper and lower exhaust ports 5 and 6. The cylinder block 2 also defines, in the lower end of the cylinder block, an exhaust outlet 7. The cylinder block partially defines an exhaust passage 8 communicating between the exhaust ports 5 and 6 and the exhaust outlet 7, and a water jacket 9 surrounding the cylinders 3 and 4 and extending adjacent the exhaust passage 8. The cylinder block includes a mounting surface 10 having mounted thereon an exhaust cover plate 11 further defining the exhaust passage 8 and the water jacket 9.
When the engine 1 is used in an outboard motor, exhaust gases flow out the exhaust ports 5 and 6, through the exhaust passage 8, and out the exhaust outlet 7 into a conventional exhaust passageway in the lower unit.